Method and apparatus for tapping furnaces



Aug. 17, 1965 J. A. HAYNES 3,201,225

METHOD AND APPARATUS FOR TAPPING FURNACES Filed 001;. 21, 1963 INVENTOR9 4 John A. Haynes ATTORNEY United States Patent O METHOD AND APPARATUS.FOR TAPPING J FURNACE John A. Haynes, Northridge, Calif assignor to letResearch Center, Inc, Arlington, Tax, a corporation of Texas Filed Oct.21', 1963, Ser. No. 317,566 11 Claims. (ill. 75-28) This inventionrelates to methods and apparatus utilizing shaped explosive charges fortapping furnaces. The invention is particularly adapted for use intapping open hearth furnaces.

O-pen hearth furnaces are generally tapped by either of two methods. Inone method an oxygen lance is used to burn through the hot metal crustatthe interior end of the furnace tap hole. In anothermethod an insulatedshaped explosive charge is used to produce a jet which pierces the hotmetal crust. The method using the insulated shaped explosive charge hasgained wide acceptance because of the increased safety to the furnaceworkmen provided there-by. A workman can initiate the tapping operationat a remote location when using the shaped explosive charge'and is notin close proximity to the exit path of molten metal as is the case whenthe oxygen lance is used to tap-the furnace.

A method and apparatus for tapping blast furnaces using 'hea-t insulatedshaped explosive charges is disclosed by Bruce Scott Old in his UnitedStates- Patent No. 2,563,131 issued August 7, 1 951, for Tapping BlastFurnaces .and the Like. .The present invention is an improvement of themethod and apparatus disclosed in the Old patent. i l i The temperatureat the end of an open hearth furnace tap hole adjacent the hot metalcrust is around 2,000 F. The high temperature severely limits the timean insulated shaped-explosive charge may remain in place'in a tap holewithout heat causing auto-detonation of the electric It is anotherobject of thisinvention to provide a method of tapping an openhearthfurnace using a shaped explosive charge apparatus wherein the apparatusmay be placed in the tap hole and left for an extended period of timewithout damage totheapparatu's.

It is also an object of this invention-to provide a shaped explosivechargeapparatus that may be used after long exposure tohightemperatures. V

It is a further-object ofthis invention to provide "a shaped explosivecharge apparatus that maybe placed in the tap hole of an open hearthfurnace andleft for an extended period of time without damage to theapparatus.

The foregoing andother objects of the invention as may appearhereinafter are realized in one aspect in a method of tapping a furnacehaving a tap hole extending through a wall of the furnace and a plugclosing the tap hole. The furnace contains a body of molten metal and alayer of crust lying against the inner end of the plug and the innersurface of the furnace wall contiguous to the plug. The method includesthe steps of removing at least a portion of the plug to provide anelongated opening; positioning a shaped explosive charge in the openingwith the jet-forming end of the charge facing the inner end of theopening; passing innocuous gas at high A misfire of the tapping chargere ice velocity over the charge to cool the same; and detonating thecharge to form a jet that pierces the solid material between the innerend of the opening and the body of molten metal to provide communicationbetween the in terior of the furnace and the opening to allow the moltenmetal to drain from the furnace.

The objects of the invention relating to the apparatus aspects arerealized in an apparatus for tap-ping a furnace or the like, whichincludes an elongated hollow housing. A shaped explosive charge iscontained within the housing adjacent one end thereof. Means is providedthat is adapted to direct .aflow of innocuous gas through the housingand over the charge to cool the charge. Means .to detonate the shapedexplosive charge is also provided.

Other objects, advantages and features of the invention will be apparentfrom a reading of the following description when taken in conjunctionwith the accompanying drawings wherein:

FIGURE I is a sectional elevation view of an open hearthfurnace with thetap hole plug drilled out and an apparatus constructed in accordancewith the invention for tapping the furnace in place in the opening inthe tap .the tap hole plug 14.

hole;

FIGURE 2 is a longitudinal sectional view of one em-' 7 FIGURE 4 is alongitudinal sectional view of another:

embodiment of a shaped charge explosive apparatus constructed inaccordance with the present invention; and

FIGURE 5 is a longitudinal sectional view of an exemplary shapedexplosive charge unit suitable for use in the apparatus illustrated inFIGURES 2 and 4.

. Referring now to FIGURE 1, the open hearth furnace, designatedgenerally by the numeral 10, has a metal sidewall 141 lined on theinterior with firebr-ick '12. The floor (not shown) of the furnace isalso lined with fire, brick .12. A tap hole 13 is provided which extendsthrough the sidewall 1-1 and the firebrick 12 lining of the furnacetothe interior of the furnace. filled with a dolomite or fire-clay plug 14be fore the furnace is charged. The heat from the furnace hardens theplug and prevents the molten metal 15 from flowing out of the tap hole13. A solid crust 16 of metal builds.

up during operation of the furnace on the fir'e'brick 12 [forming thesides and bottom of the furnace. A portion of the crust 16overliestheinner. end 17 of the tap: hole pug V The method of tappingthe furnace according to the present invention is carried out by makinga hole 18 'in The hole 18 may not extend I completely through the plug14, butis terminated about 6'to 8 inches short of the outer face of thecrust 16 which overlies the inner end 17 of the tap-hole plug. These fewinches of solid plug prevent the molten metal 15 from breaking throughthe crust '17 over the taphole in case the crust has a thin spottherein. The cuttings of dolomite are blown from the hole 18 by a streamof compressed air. A shaped explosive charge tapping ap paratus,designated generally 19, is inserted in the hole 18 in the dolomite plug14. A high velocity stream of innocuous gas,- which may be compressedair, nitrogen,

or other unreactive gas, .is supplied to the tapping app'aratus'by meansof a flexible hose 20 to keep the shaped explosive charge unit (to bedescribed hereinafter) cool.

When the molten metal 15 reaches the desired metals.

l urgical composition electric current is applied through a pair of leadwires 21 to detonate the shaped explosive charge. The jet stream formedby the detonating shaped charge penetrates the solid plug of dolomitesealing the The tap hole is.

3 inner end 17 of the tap hole and the crust 16 of red hot metaloverlying the end of the tap hole permitting the molten metal to drainthrough the opening 18 in the dolomite plug into a ladle (not shown)positioned at the front of furnace.

Referring now to FIGURE 2, one embodiment of a shaped explosive chargeapparatus 19 constructed in accordance with the present invention isillustrated. The apparatus has an elongated, hollow, cylindrical outerhousing 22 which is closed on its forward end by a friction-fitcylindrical cap 23. An elongated, hollow, cylindrical inner housing 24is mounted coaxially within the outer housing. The inner housing has asmaller diameter than does the outer housing and is slightly shorter inlength than the outer housing. A U-shaped, friction-fit annular end cap25 joins the rear ends of the inner and outer housings and also servesto space the inner housing from the outer housing. The forward end ofthe inner housing terminates short of the end cap 23 and is supportedcentrally within the outer housing by a series of spaced Z brackets 26as may be more clearly seen in FIGURE 3. These brackets may be spotwelded to the inner and outer housings, or they may be attached byscrews or other means. The rigid mounting of the smaller inner housinginside the larger diameter outer housing provides a uniform annularspace 27 between the two housings extending from the rear of the twohousings to the forward end of the inner housing. A short collar 28surrounds a small gas inlet opening 29 in the wall of the outer housingadjacent its rear end. One end of a flexible hose is fitted over thecollar to supply compressed gas to'the apparatus.

' A shaped charge explosive unit, designated generally 30, is mountedcoaxially within the inner housing 24 adjacent its forward end by meansof a series of spaced Z brackets 26a. The Z brackets support a mountingring 31 which has an inside diameter adapted to receive the shapedcharge explosive unit 30 in a close sliding fit. An electric blastingcap 32 is mounted at the rear of the shaped charge unit 30. A pair oflead wires 21 extends from the blasting cap through the open rear end ofthe inner housing to a source of electric current. The arrows shown inFIGURE 2 give the direction of the gas flow through the apparatus whenit is in place in a hot tap hole. Compressed gas at or near ambienttemperature fiows at high velocity from hose 20 into the annular space27 between the inner and outer housings, thence to the forward end ofthe outer housing where it strikes the end cap 23 which reverses thedirection of the flow causing the gas to pass over and around the shapedcharge unit 30 to cool the unit. The cap 23 also serves as a deflectorto cause a portion of the gas to impinge on the hollow face of thecharge unit 30 to cool the liner. The gas is then exhausted to theatmosphere through the open rear end of the inner housing.

The inner and outer housings 22, 24 and the end caps 23, of theapparatus are preferably made from light gage sheet metal. The housings23, 25 may consist of suitable lengths of a commercially available stovepipe or gutter drain pipe. Since the apparatus is designated tobeexpendable, it is desirable to used the most economical materials forconstructing the device consistent with the requirement that thematerials be able.

to survive exposure to the 2,000 F. temperature without damage. The heatinsulation properties of the material of construction is not criticalsince the apparatus functions by removing the heat from the shapedcharge unit by cooling with high velocity gas rather than attempting toprevent the heat from the tap hole reaching the charge unit by providinginsulating material around the charge unit,

Referring now to FIGURE 5, a shaped charge explosive unit 30 adapted foruse in the tapping apparatus and method of the present invention isillustrated. The unit has a cylindrical case 33 open at the forward orjetforming end thereof. The case may be made of metal, plastic or othersuitable material. The case contains a detonating explosive charge 34which is preferably highly compressed desensitized cyclonite(cyclotrimethylenetrinitramine). Cyclonite has a relatively high meltingpoint, (399 F.) compared to most other commercially available detonatingexplosives. A pellet of booster explosive 35 surrounds the portion ofthe integrally formed detonator cup 36 which extends into the hollow ofthe case 33 at the rear thereof. An electric blasting cap 32 is seatedin the detonator cup. A thin conical metal liner 37 is seated againstthe conical wall 38 defining the cavity in the forward end of theexplosive charge 34.

Referring now to FIGURE 4, another embodiment of a shaped explosivecharge apparatus 19a constructed in accordance with the invention isillustrated. This form of apparatus has only a single housing 24a havingabout the same diameter and length as the inner housing 24 of theapparatus shown in FIGURE '2. A shaped charge unit 30 is received in amounting ring 31 supported by Z brackets 26a positioned on the insidewall of the housing adjacent the forward open end of the housing. Therear end of the housing is closed by an end cap 25a, which may beintegrally formed with the housing or in the form of a friction-fit capsuch as shown in FIGURE 2. The end cap is provided with an axial gasinlet oepning 29a surrounded by an upstanding collar 28a which receivesthe end of a flexible hose 26 to supply compressed gas to the housing tocool the shaped charge unit. A bulkhead electrical connector 39 carriesthe pair of electrical leads 21 through the end cap 25a. A series ofJ-shaped gas deflectors 40 are attached to the inner wall of the housingimmediately forward of the shaped charge unit. These deflectors act toreverse the direction of a portion of the cooling gas flowing in fromthe rear of the apparatus to cause the gas to impinge directly on themetal liner 37 of the charge unit 30 to remove heat therefrom. When theapparatus is placed in a tap hole in a furnace and compressed gas issupplied thereto, the gas will flow in the rear of the housing24a'forwardly over the shaped charge unit 30 to cool the same, out theforward end of the housing, strike the end 17 of the tap hole plug 14and then flow back out the hole 18 in the tap hole plug to theatmosphere. The direction of gas flow is indicated by the arrows inFIGURE 4.

It can be seen from the foregoing description and drawing that animproved method and apparatus for tapping blast furnaces and the like isprovided which results in greater safety to the furnace workmen anddecreases the chance of misfire resulting from overheating of theexplosive material in the apparatus.

While the apparatus aspects of the present invention have been describedwith particular reference to use in tapping of open hearth furnaces andthe like, such use is not exclusive. The shaped charge explosive devicesof the present invention are suitable for use in any high temperatureenvironment. One other use to which the devices are adapted is theperforation of the above ground section of the casing of 'a burning oilor gas well in order to provide an opening below the flame level whichcan be used to introduce fire extinguishing material (water, foam, etc.)to extinguish the fire or to pump mud into the well bore to kill thewell. Another use of the apparatus of the present invention inperforating a burnmg storage tank to drain the flammable material fromthe tank into a surrounding fire pit where the material icianbe morereadily covered with foam toextinguish the It is understood that themethod and apparatus described herein are subject to wide modificationswithout departing from the spirit of the invention. Accordingly, thespecific methods and apparatus described are to be considered merelyillustrative and not as restricting the scope of the following claims.

I claim: 1

1. The method of tapping a furance having a tap hole extending through awall of the furnace and a plug closing the tap hole, said furnacecontaining a body of molten metal and a layer of crust lying against theinner end of end of the plug and the inner surface of the furnace wallcontiguous to the plug, which comprises:

(a) removing at least a portion of said plug to providean elongatedopening therein;

(b) positioning a shaped explosive charge in said opening with thejet-forming end of said charge facing the inner end of'said opening; (c)passing a stream of innocuous gas at high velocity over said charge tocool the same; and l (d) removing said stream of gas from the zone ofsaid charge; and

(e) detonating said charge to form a jet that pierces the solid materialbetween the inner end of said opening and said body. of molten metal toprovide communication between the interior of said furnace and saidopening to allow said molten metal to drain from saidfurnace.

2. The method of tapping a furnace having a tap hole extending through awall of the furnace and a plug closing the tap hole, said furnacecontaining a body of molten metal and a layer ofcrust lying against theinner end of the plug and the inner surface of the furnace wallcontiguous to the plug, which comprises: rv r (a) removing at least aportion of said plugto provide an elongated opening therein;

(b) positioninga shaped explosive charge in said opening with thejet-forming end of said charge facing the inner end of said opening,said charge being spaced laterally from 'the'adjacent walls of saidopening to permit substantially free flow of gas over said charge;

(c) passing a stream of innocuous gas at.high velocity over said chargeto cool'the same; and

(d) removing said'stream of r gas from the zone of said charge; and v(e) detonating said charge to form a jet that pierces the solid materialbetween the inner end of said opening and said body of molten metal toprovide communication between the interior of said furnace and saidopening to allow said molten metal to drain from said furnace.

3. The method of tapping a furnace having a tap hole extending through awall of the furnace and a plug closing the tap hole, said furnacecontaining a body of molten metal and a layer of crust lying against theinner end of the plug and the inner surface of the furnace wallcontiguous to the plug, which comprises:

(a) removing at least a portion of said plug to provide an elongatedopening therein;

(b) positioning a shaped explosive charge in said opening with thejet-forming end of said charge facing the inner end of said opening;

(c) providing an inlet conduit to conduct a flow of innocuous gas fromthe exterior of said opening to the space surrounding said charge;

(d) providing an outlet conduit to conduct a flow of innocuous gas fromsaid space surrounding said charge to the exterior of said opening;

(e) passing ,a stream of innocuous gas at high velocity into said inletconduit, over said charge, and out said outlet conduit to cool saidcharge; and

(f) detonating said charge to form a jet that pierces the solid materialbetween the inner end of said opening and said body of molten metal toprovide communication between the interior of said furnace and saidopening to allow said molten metal to drain from said furnace.

4. The method of tapping a furnace having a tap hole extending through awall of the furnace and a plug closing the tap hole, said furnacecontaining a body of molten metal and a layer of crust lying against theinner end of the plug and the inner surface of the furnace wallcontiguous to the plug, which comprises:

(a) removing at least a. portion of said plug to provide an elongatedopening therein;

r (b) positioning a shaped explosive charge in said opening with the jetforming end of said charge facing the inner end of said opening, saidjet forming end of said charge providing a cavity therein, the wall ofsaid charge forming said cavity being lined with a metal liner;

(c) passing a stream of innocuous gas at high velocity over said chargeto cool the same;

(d) deflecting at least a portion of said stream of innocuous gas intodirect contact with said metal liner to cool said liner; I a

(e) removing said stream of gas from the zone of said charge; and V j, r

(f) detonating said charge to form a jet that pierces the solid materialbetween the inner end of said opening and said body of molten metal toprovide communication between the interior of said furnace and saidopening to allow said molten metal to drain from said furnace. I

5. An apparatus for tapping a furnace and the like comprising:

. (a) an elongated hollow housing;

. (b) a shaped explosive charge within said housing adjacent one endthereof; i

(c) means for directing a flow of innocuous gas through said housing andover said charge for cooling said charge; and v o (d) means fordetonating said shaped explosive charge.

6. An apparatus for tapping a furnace and the like comprising:

(a) an elongated hollow housing;

j (b) a shaped explosive chargewithin said housing adjacent one endthereof, said charge having its jetforming end facing said adjacent endof said housing;

(c) means coupled to the other end of said housing for directing a flowof innocuous gas through said housing and over said charge for coolingsaid charge; and

(d) means for detonating said shaped explosive charge.

7. An apparatus for tapping a furnace and the like comprising:

(a) an elongated hollow housing;

(b a shaped explosive charge within said housing adacent one endthereof, said charge having its jetforming end facing said adjacent endof said housing;

(c) means mounting said charge within said housing for permittingsubstantially free flow of innocuous gas over said charge;

(d) means for directing a flow of innocuous gas through said housing andover said charge for cooling said charge; and

(e) means for detonating said shaped explosive charge.

8. apparatus for tapping a furnace and the like comprlsmg:

(a) an elongated hollow housing having an end closure at one endthereof;

(b) a shaped explosive charge within said housing, said charge beingspaced from but adjacent to said end closure and having its jet-formingend facing said end closure;

(c) means mounting said charge within said housing, said means laterallyspacing said charge from the inner walls of said housing for permittingsubstantially free flow of innocuous gas over said charge;

((1) conduit means attached to said housing for delivering a flow ofinnocuous gas into the space between said end closure and jet-formingend of said charge and thence over said charge for cooling the same; and

(e) means for detonating said shaped explosive charge.

9. An apparatus for tapping a furnace and the like comprising:

(a) an elongated hollow outer housing having an end closure at one endthereof;

(b) an elongated hollow inner housing mounted substantially within saidouter housing, said inner housing having its outside walls spacedlaterally from the inner walls of said outer housing and having one endterminating short of said end closure;

(c) a shaped explosive charge within said inner housing near that end ofsaid inner housing which is adjacent said end closure, said chargehaving its jet forming end facing said end closure;

(d) means mounting said charge within said inner housing for permittingsubstantially free flow of innocuous gas over said charge for coolingsaid charge;

(e) means for directing a flow of innocuous gas through said housingsand over said charge for cooling said charge; and

(f) means for detonating said shaped explosive charge.

10. An apparatus for tapping a furnace and the like comprising:

(a) an elongated hollow generally cylindrical outer 7 housing, saidhousing having at least one of its ends closed;

(b) an elongated hollow generally cylindrical inner housing mountedsubstantially within said outer housing, said inner housing having itsoutside walls spaced laterally from the inner walls of said outerhousing and being open on both ends, one of said open ends terminatingshort of said closed end of said outer housing, the other end beingsealed to said outer housing by a ring-shaped end wall;

(c) a shaped explosive charge within said inner housing near that end ofsaid inner housing which terminates short of the closed end of saidouter housing, said charge having its jet-forming end facingthe closedend of said outer housing;

(d) means mounting said charge coaxially within said inner housing forpermitting substantially free flow of innocuous gas over said charge;

(e) conduit means connected to said outer housing for introducing a flowof innocuous gas from an external source into the annular space betweensaid housings, whereby the gas will flow through the annular spacearound the open end of said inner housing and over the shaped explosivecharge for cooling said charge; and

(f) means for detonating said shaped explosive charge.

11. An apparatus for tapping a furnace and the like comprising:

(a) an elongated hollow housing;

(b) a shaped explosive charge within said housing adjacent one endthereof, said charge having its jetforming end facing said adjacent endof said housing;

(c) means mounting said charge within said housing for permittingsubstantially free flow of innocuous gas over said charge;

(d) means attached to said housing for directing a flow of innocuous gasthrough said housing and over said charge for cooling said charge;

(e) deflector means located forwardly of the jet-forming end of saidcharge for deflecting a portion of said gas to impinge on said jetforming end of said charge; and

(f) means for detonating said shaped explosive charge.

References Cited by the Examiner UNITED STATES PATENTS 748,935 1/04Dunham 10224 2,563,131 8/51 Old 41 2,847,205 8/58 Hnilicka 7584.5

DAVID L. RECK, Primary Examiner.

WINSTONA. DOUGLAS, Examiner.

1. THE METHOD OF TAPPING A FURANCE HAVING A TAP HOLE EXTENDING THROUGH AWALL OF THE FURNACE AND A PLUG CLOSING THE TAP HOLE, SAID FURNACECONTAINING A BODY OF MOLTEN METAL AND A LAYER OF CRUST LYING AGAINST THEINNER END OF END OF THE PLUG AND THE INNER SURFACE OF THE FURNACE WALLCONTIGUOUS TO THE PLUG, WHICH COMPRISES; (A) REMOVING AT LEAST A PORTIONOF SAID PLUG TO PROVIDE AN ELONGATED OPENING THEREIN; (B) POSITIONING ASHAPED EXPLOSIVE CHARGE IN SAID OPENING WITH THE JET-FORMING END OF SAIDCHARGE FACING THE INNER END OF SAID OPENING; (C) PASSING A STREAM OFINNOCUOUS GAS AT HIGH VELOCITY OVER SAID CHARGE TO COOL THE SAME; AND(D) REMOVING SAID STREAM OF GAS FROM THE ZONE OF SAID CHARGE; AND (E)DETONATING SAID CHARGE TO FORM A JET THAT PIERCES THE SOLID MATERIALBETWEEN THE INNER END OF SAID OPENING AND SAID BODY OF MOLTEN METAL TOPROVIDE COMMUNICATION BETWEEN THE INTERIOR OF SAID FURNACE AND SAIDOPENING TO ALLOW SAID MOLTEN METAL TO DRAIN FROM SAID FURNACE.